Portable propane-fueled battery charger

ABSTRACT

System and method for a portable propane-fueled battery charger. One system includes a battery charger including a propane fuel line and an engine including an output shaft. The engine is configured to receive propane via the propane fuel line and rotationally drive the output shaft. The battery charger further includes an alternator including a rotor and stator coils. The output shaft is mechanically coupled to the rotor, and the rotor is rotationally driven by the output shaft. An electrical current is induced in the stator coils by rotation of the rotor. The battery charger further includes an electrical circuit that receives the electrical current and is configured to determine when a battery pack is coupled to a battery connector, and charge the battery pack.

RELATED APPLICATIONS

The present application is a continuation application of U.S.Non-provisional application Ser. No. 15/093,397, filed Apr. 7, 2016,which claims priority to U.S. Provisional Application 62/143,952, filedApr. 7, 2015, the entire contents of which are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to portable battery chargers.

SUMMARY

Embodiments of the invention provide a portable propane-fueled batterycharger. The charger includes a propane-fueled engine that drives analternator to generate electrical power output. The power output by thealternator is used to charge one or more battery packs coupled to thecharger.

One embodiment provides a battery charger including a propane fuel lineand an engine including an output shaft. The engine is configured toreceive propane via the propane fuel line and rotationally drive theoutput shaft. The battery charger further includes an alternatorincluding a rotor and stator coils. The output shaft is mechanicallycoupled to the rotor, and the rotor is rotationally driven by the outputshaft. An electrical current is induced in the stator coils by rotationof the rotor. The battery charger further includes an electrical circuitthat receives the electrical current and is configured to determine whena battery pack is coupled to a battery connector, and charge the batterypack.

Another embodiment provides a method of charging a battery pack. Themethod includes receiving, by an engine, propane via a propane fuelline. The method further includes starting the engine and rotationallydriving an output shaft of the engine. The output shaft is mechanicallycoupled to a rotor of an alternator. The method further includesinducing an electrical current in stator coils of the alternator andproviding the electrical current to an electrical circuit. The methodfurther includes determining, with the electrical circuit, that thebattery pack is coupled to a battery connector, and charging, with theelectrical circuit, the battery pack.

Another embodiment provides a battery charger including a first platethat supports a propane engine and an alternator. The propane engine isconfigured to drive the alternator, and the alternator is configured toprovide an electrical current to an electrical circuit. The batterycharger further includes a second plate that supports the electricalcircuit and the first plate. The electrical circuit is configured tocharge a battery pack. The battery charger further includes a housingincluding a lower housing portion and an upper housing portion. Theupper housing portion houses the alternator, and the lower housingportion includes a plurality of battery connectors coupled to theelectrical circuit to receive charging current.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a first perspective view of a portable propane-fueledbattery charger according to embodiments of the invention.

FIG. 2 illustrates a second perspective view of the portablepropane-fueled battery charger of FIG. 1.

FIG. 3 illustrates a side view of the portable propane-fueled batterycharger of FIG. 1.

FIG. 4 illustrates a top view of the portable propane-fueled batterycharger of FIG. 1.

FIG. 5 illustrates a third perspective view of a portion of the portablepropane-fueled battery charger of FIG. 1.

FIG. 6 illustrates a perspective side view of a portion of the portablepropane-fueled battery charger of FIG. 1 with a clam shell housingseparated.

FIG. 7 illustrates another side view of the portable propane-fueledbattery charger of FIG. 1 with a portion of the clam shell housingremoved.

FIG. 8 illustrates a power tool battery pack operable to be charged by apropane-fueled battery charger according to embodiments of theinvention.

FIG. 9 illustrates a method of operation of the propane-fueled batterycharger of FIG. 1 according to some embodiments.

FIG. 10 is a block diagram of the portable propane-fueled batterycharger of FIG. 1.

FIG. 11 is a block diagram of a portable propane-fueled battery chargeraccording to another embodiment of the invention.

FIG. 12 illustrates a portable propane-fueled battery chargercorresponding to the block diagram of FIG. 11.

FIG. 13 illustrates a method of starting an engine of the propane-fueledbattery charger of FIGS. 11 and 12 according to some embodiments.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

It should also be noted that a plurality of hardware and software baseddevices, as well as a plurality of different structural components maybe used to implement the invention. In addition, it should be understoodthat embodiments of the invention may include hardware, software, andelectronic components or modules that, for purposes of discussion, maybe illustrated and described as if the majority of the components wereimplemented solely in hardware. However, one of ordinary skill in theart, and based on a reading of this detailed description, wouldrecognize that, in at least one embodiment, the electronic based aspectsof the invention may be implemented in software (e.g., stored onnon-transitory computer-readable medium) executable by one or moreprocessors. As such, it should be noted that a plurality of hardware andsoftware based devices, as well as a plurality of different structuralcomponents may be utilized to implement the invention. Furthermore, andas described in subsequent paragraphs, the specific mechanicalconfigurations illustrated in the drawings are intended to exemplifyembodiments of the invention and that other alternative mechanicalconfigurations are possible. For example, “controllers” described in thespecification can include standard processing components, such as one ormore processors, one or more computer-readable medium modules, one ormore input/output interfaces, and various connections (e.g., a systembus) connecting the components.

FIGS. 1-7 show a portable, propane-fueled battery charger 100 (charger100). The charger 100 includes a clamshell housing 102 having a lowerhousing portion 104 and an upper housing portion 106. The lower housingportion 104 includes six battery connectors 108 a-f (collectively,battery connectors 108), a propane tank bracket 110 (a propane tankholder), an on/off toggle switch 112, and a universal serial bus (USB)data port 114. The USB data port 114 enables an external device toconnect to and program a microcontroller of the charger 100 (e.g., theMCU 202 of FIG. 9). Each battery connector 108 is associated with acharge indicator 115. The propane tank bracket 110 holds a propane tank116. A carrying handle 118 extends out of through-holes in the lowerhousing portion 104 and over the top of the upper housing portion 106.

Turning to FIG. 7, the upper housing portion 106 partially encloses apropane-fueled internal combustion engine 120 (propane engine 120) andan alternator 122. The alternator 122 is mounted to the propane engine120 via a mounting bracket 124. The propane engine 120 is mounted to anupper support plate 126. The upper support plate 126 is mounted to foursupport columns 128 that abut the bottom surface of the upper supportplate 126 at a substantially perpendicular angle. At their oppositeends, each of the four support columns 128 abut a base plate 130 at asubstantially perpendicular angle. Accordingly, the upper support plate126 and the base plate 130, which are substantially planar, formsubstantially parallel planes. As illustrated, the upper support plate126 and the base plate 130 are substantially horizontal, while the foursupport columns 128 are substantially vertical. The base plate 130provides support for the four support columns 128 and, therefore, theupper support plate 126. The base plate 130 includes four feet 132 onwhich the base plate 130 and other components of the charger 100ultimately rest. The attaching portions of the carrying handle 118 aresecured to opposite ends of the base plate 130 and pass through cutoutsof the upper support plate 126 before extending out of the lower housingportion 104. A lower portion of the propane tank bracket 110 is securedto the base plate 130 and an upper portion of the propane tank bracket110 is secured to the upper support plate 126.

The base plate 130, support columns 128, and upper support plate 126 areconstructed of metal. The metal construction provides a strong supportstructure, and the metal has a high thermal transfer property comparedto, e.g., plastic. As illustrated in, for instance, FIG. 3, when fullyassembled, a top surface of the upper support plate 126 is exposedthrough a cut-out of the upper housing portion 106 to the ambientenvironment. The exposure of the metal surface of the upper supportplate 126 aids in transferring thermal energy generated within thehousing 102 to the ambient environment. For instance, the heat generatedby an electrical circuit 134 between the upper support plate 126 and thebase plate 130 is transferred to the ambient environment (air) by thecombination of the base plate 130, support columns 128, and uppersupport plate 126. In other words, the combination of the base plate130, support columns 128, and upper support plate 126 provides heatsinking for the charger 100. Additionally, the upper support plate 126is a barrier that blocks air from the engine 120 from reaching theelectrical circuit 134. The electrical circuit 134 includes for example,one or more printed circuit boards, microcontrollers, interconnectingwires, charging circuits, interconnecting wires, and additionalcircuitry, and is described in further detail below with respect toFIGS. 10 and 11.

Each battery connector 108 is configured to receive a power tool batterypack 150 (see FIG. 8). In the illustrated embodiment, the battery pack150 is a slide-on style battery pack. Accordingly, each batteryconnector 108 includes guide rails/grooves to receive reciprocal guiderails/grooves of the battery pack 150. In other embodiments, one or moreof the battery connectors 108 are configured to receive tower-stylebattery packs or other styles of battery packs for charging. In additionto the mechanical coupling aspects (e.g., guide rails/grooves) thatallow a user to selectively secure the battery pack 150 to the charger100, each battery connector 108 includes terminals for electricallyconnecting a coupled battery pack to the electrical circuit 134.

The terminals for the battery pack 150 include a positive and a negativeterminal to provide power to and from the battery pack 150. In someembodiments, the battery pack 150 also includes a temperature terminalto allow the charger 100 or a power tool to monitor the temperature ofan attached battery pack 150. In some embodiments, the battery pack 150also includes data terminals to communicate with the charger 100 or anattached power tool. For example, the battery pack 150 may include amicrocontroller to monitor one or more characteristics of the batterypack 150 and the data terminals may communicate with the charger 100regarding the monitored characteristics.

The charge indicator 115 associated with each battery connector 108signals a charge status of a battery pack connected to that particularbattery connector 108, such as charging, fully charged, or faultpresent. For example, the charge indicator 115 includes two LEDs. In oneembodiment, the LEDs may be of different colors, for example green andred. The charge indicator 115 may then show that the battery pack 150 ischarging by, for example, flashing a red LED. Alternatively, the chargeindicator 115 may show that the battery pack 150 is completely chargedby, for example, lighting a green LED.

The battery pack 150 is a power tool battery pack generally used topower a power tool, such as an electric drill, an electric saw, and thelike. In some embodiments, each battery pack 150 includes amicrocontroller that monitors characteristics of the battery pack 150.For example, the microcontroller may monitor the state of charge of thebattery pack 150, the temperature of the battery pack 150, or othercharacteristics relevant to the battery pack 150. The microcontrollermay also control aspects of charging and/or discharging of the batterypack 150. In the illustrated embodiment, the battery pack 150 alsoincludes an indicator 152 on the face of the battery pack 150 to displaythe current state of charge of the battery pack 150 and/or othercharacteristics of the battery pack 150. In the illustrated embodiment,the indicator 152 includes a plurality of LEDs. As the state of chargeof the battery pack 150 increases, more LEDs light up and as the stateof charge of the battery pack 150 decreases, less LEDs light up. Thebattery pack 150 may include a different type of indicator to displaythe state of charge of the battery. For example, the indicator 152 mayinclude a single LED that lights up only when the battery pack 150 isfully charged. In other embodiments, the battery pack 150 does notinclude an indicator.

In the illustrated embodiments, the battery packs 150 include lithiumion cells. In other embodiments, the battery packs 150 may be of adifferent chemistry, for example, nickel-cadmium, or nickel-hydride. Inthe illustrated embodiment, the battery pack 150 is an 18 volt battery.In other embodiments, the capacities of the battery packs configured tobe charged by the charger 100 are different. For example, the batterypacks can be 4 volt battery packs, 12 volt battery packs, 28 voltbattery packs, 40 volt battery packs, or another voltage.

FIG. 9 illustrates a method 900 of operation of the charger 100. Atblock 905, the engine 120 receives propane from the propane tank 116 viaa fuel line 140 and a valve 142. The propane engine 120 includes arecoil/pull starter 144 that a user pulls to start the propane engine120 (at block 910). Alternatively, in some embodiments, the charger 100may include a pushbutton switch 252 (FIGS. 11 and 12) that is used tostart the propane engine 120 as explained in greater detail below (FIG.13). The propane received through the fuel line 140 is combusted viaspark ignition to provide motive force to pistons that is mechanicallytranslated to rotationally drive an output shaft (at block 915). Theoutput shaft is mechanically coupled to a permanent magnet rotor of thealternator 122, such that the rotor is rotationally driven by the outputshaft of the propane engine 120 (also at block 915). The rotatingmagnets of the rotor induce current in the stator coils of thealternator 122 that are positioned around the rotor (at block 920). Thecurrent induced in the stator coils is then fed into the electricalcircuit 134 between the upper support plate 126 and base plate 130 (atblock 925). The electrical circuit 134 determines whether a battery pack(e.g., the battery pack 150) is coupled to one or more of the batteryconnectors 108 (at block 930). For example, the electrical circuit 134may determine that a battery pack is coupled to one of the batteryconnectors 108 in response a signal provided by the battery pack overthe battery connector 108 to the electrical circuit 134 or in responseto a change in a characteristic (e.g., voltage level) on a terminal ofthe battery connectors 108 in response to coupling of a battery packthereto. The electrical circuit 134 further includes charging circuitrythat charges the battery pack by supplying current provided by thealternator 122 to the battery pack (at block 935).

As explained in greater detail below, in some embodiments, the charger100 may charge two battery packs simultaneously. Furthermore, in someembodiments, at block 930, the electrical circuit 134 may determinewhich of the battery connectors 108 are coupled to battery packs 150and, the in step 935, may provide charging current to at least one ofthe battery packs 150. In some embodiments, at block 935, the charger100 may continue to charge the battery pack 150 until the battery pack150 is fully charged. As explained in greater detail below, when thebattery pack 150 is fully charged, the charger 100 may begin charginganother battery pack that is coupled to one of the battery connectors108. Furthermore, in some embodiments, the charger 100 may continue tocharge the battery pack 150 until the electrical circuit 134 receives asignal that indicates a different battery pack should be charged (e.g.,a signal from sequence switches 160 and 162) as explained in greaterdetail below.

As noted above, the charger 100 includes an on/off toggle switch 112(see, e.g., FIG. 1). Referring back to FIG. 9, in some embodiments, theelectrical circuit 134 determines the position of the on/off toggleswitch 112 to determine whether the propane engine 120 is started atblock 910. When in the “off” position, the on/off toggle switch 112prevents or breaks an electrical connection between a spark plug of thepropane engine 120 and/or a power source and between circuit boards ofthe charger 100 and a power source (e.g., one of the battery packs 150coupled to one of the battery connectors 108). When in the “on”position, the on/off toggle switch 112 makes or no longer prevents oneor both of these electrical connections. Accordingly, in someembodiments, the method 900 does not start the propane engine 120 atblock 910 unless the on/off toggle switch 112 is in the “on” position.

Turning to FIG. 2, the upper housing portion 106 includes a leftsequence switch 160 and a right sequence switch 162. The left sequenceswitch 160 is associated with battery connectors 108 d-f, while theright sequence switch 162 is associated with battery connectors 108 a-c.The electrical circuit 134 of the charger 100 includes two chargingcircuits, one associated with battery connectors 108 d-f and the otherassociated with battery connectors 108 a-c (see, e.g., FIG. 10). At agiven moment, the charger 100 is operable to supply charging current toone of the three battery connectors 108 a-c and one of the three batteryconnectors 108 d-f Accordingly, the charger 100 is operable tosimultaneously charge two battery packs 150. The right sequence switch162 is a push-button that enables a user to cycle through and selectwhich one of the battery packs 150 coupled to the battery connectors 108a-c is to be charged, while the left sequence switch 160 is apush-button that enables a user to cycle through and select which one ofthe battery packs 150 coupled to the battery connectors 108 d-f is to becharged. After a battery pack 150 is fully charged, the chargingcircuitry will automatically cycle to the next battery pack 150 to becharged on the respective side of the charger 100.

FIG. 10 illustrates a block diagram of the charger 100 including theengine 120, alternator 122, and battery connectors 108, as well as theelectrical circuit 134 a within the housing 102. The electrical circuit134 a is an embodiment of the electrical circuit 134 and includes amicrocontroller (MCU) 202, a zero-crossing detector 206, a three-phaserectifier 208, a 75V limiter 210, a power supply 212, a left 24V switchpower supply (PS) 214, a right 24V switch PS 216, a left three-baysequence charger 218, and a right three-bay sequence charger 220.

The microcontroller (MCU) 202 sends an engine ignition signal to thepropane engine 120 and that is coupled to a throttle servo 204. Theengine ignition signal is an enable/disable signal for the engine 120.When an “enable” signal is sent, the engine 120 is able to run; when a“disable” signal is sent, the engine 120 is stopped and prevented fromrunning. The MCU 202 sends control signals to the throttle servo 204 toadjust a carburetor valve of the engine 120 and, thereby, the speed ofthe engine 120. As noted above, the engine 120 drives a rotor of thealternator 122, which induces current in stator coils of the alternator122. The current induced in and output by the stator coils is sinusoidaland provides three-phase alternating current (AC) power (one phase percoil). The output AC power is monitored by the zero-crossing detector206 and is received by the three-phase rectifier 208. The zero-crossingdetector 206 detects when the AC power crosses zero (e.g., alternatesfrom negative to positive or from positive to negative) and provides anindication of each zero crossing (e.g., via a pulse) to the MCU 202. TheMCU 202 can infer the rotational speed, e.g., rotations per minute(RPM), of the engine 120 from the timing of the indications.

The three-phase rectifier 208 converts the AC power to direct current(DC) power and provides the DC power to the 75V limiter 210. The 75Vlimiter 210 limits the DC power to 75V and provides the limited DC powerto the power supply 212, to the left 24V switch power supply (PS) 214,and to the right 24V switch PS 216. The power supply 212 conditions andoutputs 5V and 24V supply voltages to circuitry within the charger 100.For instance, although not shown, the power supply 212 outputs 5V powerto the MCU 202 to power the MCU 202.

The left and right 24V power supplies 214 and 216 condition the receivedDC power from the 75V limiter 210 and provide DC power at a leveldetermined by voltage feedback received from the left three-bay sequencecharger 218 and the right three-bay sequence charger 220, respectively.For instance, when a battery pack 150 coupled to the battery connector108 f is being initially charged, the left 24V power supply 214 mayprovide a 24V supply voltage at 5 amperes (A) to the left three-baysequence charger 218. Eventually, the left three-bay sequence charger218 may provide an indication (voltage feedback) to the left 24V powersupply 214 that the battery pack 150 is getting closer to being fullycharged. In turn, the left 24V power supply 214 may reduce the currentto 3A, and then eventually to zero once the battery pack 150 is fullycharged.

The power supply 212 also outputs a 24V supply voltage to the left andright three-bay sequence chargers 218, 220 to provide power forcommunications between coupled battery packs and the sequence chargers218, 220.

The three-bay sequence chargers 218 and 220 receive a signal from theleft and right sequence switches 160 and 162, respectively, upon theirdepression by a user. In response, the three-bay sequence charger 218 or220 will cycle to its next battery connector 108 having an attachedbattery pack 150, and begin providing charging current to that batterypack 150 as appropriate depending on the pack's state of charge.

The three-bay sequence chargers 218 and 220 also provide currentfeedback to the MCU 202 indicating the amount of charging current thateach sequence charger 218 and 220 is presently outputting. In turn, theMCU 202 controls the driving of the alternator 122 by the engine 120.For instance, the MCU 202 can increase the speed of the engine 120 ifthe sequence chargers 218 and/or 220 are outputting a large amount ofcurrent and can decrease the speed of the engine 120 if a lower amountof current is being output.

For proper operation, the engine 120 should generally be upright asshown, e.g., in FIGS. 1-7. The charger 100 also includes a tilt switch222 to ensure that the engine 120 is operated in the upright or nearupright position. The tilt switch 222 outputs a first signal when thecharger 100 is upright or near upright (e.g., within 25° of upright).For instance, with reference to the charger 100 of FIGS. 1-7, when allfour feet 132 are on a level surface, the charger 100 is upright, andthe tilt switch 222 outputs a 0V DC signal to the MCU 202. When thecharger 100 is tipped over (e.g., more than 25°, the tilt switch 222outputs an indication that the charger 100 has tilted in excess of apredetermined amount. In response, the MCU 202 shuts down the engine120. In some embodiments, the tilt switch 222 outputs an analog signalrepresenting the level of tilt to the MCU 202. The MCU 202 thendetermines whether the indicated tilt level (angle) exceeds a thresholdand whether to shut down the engine 120. Accordingly, the MCU 202controls the engine 120 to stop based on an output received from thetilt switch 222.

FIG. 11 illustrates a block diagram for a portable, propane-fueledbattery charger 250 (charger 250), which is another embodiment of thecharger 100. The charger 250 is generally similar to the charger 100except for the addition of electronic starting functionality shown inFIG. 11 and the addition of a motor start pushbutton switch 252 on thehousing 102 as shown in FIG. 12. Accordingly, the description of thephysical components of the charger 100 provided with respect to FIGS.1-7 apply to the charger 250 as well. Moreover, like numbered componentsof the block diagrams in FIGS. 10 and 11 have similar functionality,unless otherwise provided below.

As shown in FIG. 11, the charger 250 includes similar components as thecharger 100 and further includes the motor start pushbutton switch 252(start switch 252), a motor drive circuit 254, and a switch 256. Thecharger 250 includes an electrical circuit 134 b, which is anotherembodiment of the electrical circuit 134 that is similar to theelectrical circuit 134 a of FIG. 10 but further includes the motor drivecircuit 254 and the switch 256. FIG. 13 illustrates a method 1300 ofstarting the propane engine 120 that may be executed by the MCU 202 as apart of block 910 of the method 900 (FIG. 9) in some embodiments. Inresponse to a user depression of the start switch 252, the start switch252 outputs an indication to the MCU 202 (at block 1305). In turn, theMCU 202 provides a start command to the motor drive circuit 254 (atblock 1310). The switch 256 includes multiple FETs that are controlledby the MCU 202 to select one of the battery connectors 108 that ispresently coupled to a battery pack 150 to the motor drive circuit 254.The MCU 202 is operable to detect whether battery packs 150 are coupledto the battery connectors 108 and the state of charge of the batterypacks 150 (at block 1315). For example, the battery packs 150 mayprovide a signal to the MCU 202 upon connector to a battery connector108 such that the MCU 202 detects the presence of the battery pack 150.Additionally, the battery packs 150 or the electrical circuit 134 b mayinclude a state of charge sensor that provides a signal indicative ofthe state of charge of the battery pack (e.g., based on a voltagemeasurement) to the MCU 202. The MCU 202 then selects one of the batterypacks 150 with a sufficient state of charge for powering thealternator/starter motor 122 (at block 1320). The MCU 202 controls theswitch 256 (via a wired communication path not shown) to make anelectrical connection between the selected battery back 150 and themotor drive circuit 254 (at block 1325). The motor drive circuit 254then drives the alternator/starter motor 122 to start the propane engine120 (at block 1330).

The motor drive circuit 254 is configured to selectively apply currentfrom the switch 256 to the stator coils of the alternator 122 to drivethe rotor. The motor drive circuit 254 may include, for instance, sixfield effect transistors (FET) in a bridge configuration. The MCU 202selectively outputs enable and disable signals to each FET toselectively apply the current from the switch 256 to the stator coils ofthe alternator 122. The selectively energized stator coils generate achanging magnetic field that drives the rotor. The rotor, in turn,drives the drive shaft of the engine 120 to assist in starting theengine 120 in a similar way as occurs through a manual pull of therecoil/pull starter 144. Thus, the alternator 122 also serves as astarting motor.

Engine spark during an initial turn over phase of the propane engine 120can result in an increased starting torque, making it difficult for thealternator/starter motor 122 to complete its starting revolutions andstart the propane engine 120. To counter this occurrence, in someembodiments, the charger 100 and 250 include an easy start mode. In theeasy start mode, the MCU 202 does not provide the engine ignition signalto the engine 120 during an initial starting period of the engine 120,which prevents sparking by a spark plug of the engine 120. In otherwords, the MCU 202 implements a spark delay. By not providing power tothe spark plug during the spark delay, less torque is needed to turn thedrive shaft to start the engine 120. Once the alternator/starter motor122 has reached a peak rotational momentum or exceeded a momentumthreshold, the spark is enabled and the engine 120 starts.

The spark delay is the time period between the MCU 202 first sendingdrive commands to the motor drive circuit 254 to start the engine 120and the MCU 202 first sending the engine ignition signal to the engine120 to power its spark plug. The spark delay is a function of themomentum of the engine 120, which can be determined via the engine speedbased on outputs of the zero-crossing detector 206. Alternatively, thespark delay may be a predetermined time period (e.g., saved in the MCU202), may be based on the number of zero crossings detected or indicatedby the zero-crossing detector 206 or a combination thereof.

Accordingly, with the easy start mode, less force is required of thealternator/starter motor 122. This reduction in required starting torqueallows a smaller alternator/starter motor 122 to be used in the charger250 than if power was provided to the spark plug of the engine 120during starting. Similar spark delay principles are applicable to amanual start using the recoil/pull starter 144, reducing the forcerequired by the user to pull the recoil/pull starter 144.

Thus, embodiments of the invention provide, among other things, aportable, propane-fueled battery charger with a propane-fueledengine-generator, the charger configured to provide power to chargepower tool battery packs.

We claim:
 1. A battery charger comprising: a housing that supports abattery connector configured to receive and support a battery pack, thebattery connector including electrical terminals configured to engageelectrical terminals of the battery pack, and a mechanical couplingconfigured to engage a mechanical interface of the battery pack; acarrying handle coupled to the housing; a propane fuel line; an engineincluding an output shaft, the engine configured to receive propane viathe propane fuel line and rotationally drive the output shaft; analternator including a rotor and stator coils, wherein the output shaftis mechanically coupled to the rotor, the rotor is rotationally drivenby the output shaft, and an electrical current is induced in the statorcoils by rotation of the rotor; and an electrical circuit that receivesthe electrical current and is configured to determine when the batterypack is coupled to the battery connector, and charge the battery packbased on the determination.
 2. The battery charger of claim 1, whereinthe battery pack is a first battery pack and the electrical circuit isconfigured to simultaneously charge a second battery pack.
 3. Thebattery charger of claim 2, further comprising a first set of batteryconnectors including the battery connector and a second set of batteryconnectors, wherein the electrical circuit is configured tosimultaneously charge the first battery pack coupled to one of the firstset of battery connectors and the second battery pack coupled to one ofthe second set of battery connectors.
 4. The battery charger of claim 3,wherein the electrical circuit is configured to charge a third batterypack coupled to the first set of battery connectors when the electricalcircuit determines that the first battery pack is fully charged.
 5. Thebattery charger of claim 3, further comprising a first sequence switch,wherein the first sequence switch is configured to selectively controlthe electrical circuit to provide a first charging current through oneof the first set of battery connectors; and a second sequence switch,wherein the second sequence switch is configured to selectively controlthe electrical circuit to provide a second charging current through oneof the second set of battery connectors.
 6. The battery charger of claim1, wherein the electrical circuit is configured to determine a state ofcharge of each of a plurality of battery packs coupled to the batterycharger; select, based on the state of charge, a selected battery packfrom the plurality of battery packs; and electrically connect theselected battery pack to a motor drive circuit, wherein the motor drivecircuit drives the alternator to start the engine.
 7. The batterycharger of claim 1, wherein the electrical circuit adjusts a speed ofthe engine based on a charging current being provided to the batterypack.
 8. The battery charger of claim 1, further comprising a tiltswitch that indicates when the battery charger is tilted in excess of apredetermined tilt threshold, wherein the electrical circuit shuts downthe engine when the tilt switch indicates that the battery charger istilted in excess of the predetermined tilt threshold.
 9. The batterycharger of claim 1, further comprising: a toggle switch; and an inputunit; wherein the engine is configured to start when the toggle switchis in a first position and the input unit is activated.
 10. The batterycharger of claim 1, further comprising a first plate that supports theengine and the alternator; and a second plate that supports theelectrical circuit, wherein the carrying handle is coupled to thehousing via a connection to the second plate and extends out ofthrough-holes in the housing, and wherein the second plate issubstantially parallel with the first plate.
 11. The battery charger ofclaim 1, further comprising a second battery connector coupled to theelectrical circuit, wherein the housing encloses the electrical circuitand includes a first side face and a second side face, the electricalcircuit is positioned between the first side face and the second sideface, the battery connector is positioned on the first side face of thehousing, and the second battery connector is positioned on the secondside face of the housing.
 12. A method of charging a battery pack, themethod comprising: receiving and supporting, by a battery connector of ahousing, the battery pack, the battery connector including electricalterminals that engage electrical terminals of the battery pack, and amechanical coupling that engages a mechanical interface of the batterypack; receiving, by an engine, propane via a propane fuel line; startingthe engine; rotationally driving an output shaft of the engine, theoutput shaft being mechanically coupled to a rotor of an alternator;inducing an electrical current in stator coils of the alternator by therotational driving of the output shaft; providing the electrical currentto an electrical circuit in the housing; determining, with theelectrical circuit, that the battery pack is coupled to the batteryconnector; and charging, with the electrical circuit, the battery pack.13. The method as claimed in claim 12, wherein the battery pack is afirst battery pack, the method further comprising charging, with theelectrical circuit, a second battery pack.
 14. The method as claimed inclaim 13, wherein charging, with the electrical circuit, the firstbattery pack includes charging, with the electrical circuit, the firstbattery pack when the first battery pack is coupled to a first set ofbattery connectors, and wherein charging, with the electrical circuit,the second battery pack includes charging, with the electrical circuit,the second battery pack when the second battery pack is coupled to asecond set of battery connectors.
 15. The method as claimed in claim 14,further comprising charging, with the electrical circuit, a thirdbattery pack coupled to the first set of battery connectors when theelectrical circuit determines that the first battery pack is fullycharged.
 16. The method as claimed in claim 14, further comprising:selectively controlling, with a first sequence switch, the electricalcircuit to provide a first charging current through one of the first setof battery connectors; and selectively controlling, with a secondsequence switch, the electrical circuit to provide a second chargingcurrent through one of the second set of battery connectors.
 17. Themethod as claimed in claim 12, wherein starting the engine furthercomprises: electrically connecting, with the electrical circuit, thebattery pack to a motor drive circuit; and driving, with the motor drivecircuit, the alternator to start the engine.
 18. The method as claimedin claim 12, further comprising adjusting a speed of the engine based ona charging current being provided to the battery pack.
 19. The method asclaimed in claim 12, further comprising: determining, with a tiltswitch, when a battery charger is tilted in excess of a predeterminedtilt threshold; and shutting down the engine, with the electricalcircuit, when the tilt switch indicates that the battery charger istilted in excess of the predetermined tilt threshold.
 20. The method asclaimed in claim 12, wherein starting the engine includes receiving,from a toggle switch, a toggle switch signal indicative of a position ofthe toggle switch; receiving, from an input unit, a start engine signal;and when the toggle switch signal indicates that the toggle switch is ina first position, starting the engine.